Method of and apparatus for utilization of observable radiations



L. BELL'AND MARSHALL.

METHOD OF AND APPARATUS FOR UTILIZATION OF OBSERVABLE RADIATIONS.

APPLICATION FILED MAR. 4. 191a.

. 1 3 5 657. Patented July 26, 1921.

2 SHEETS-SHEET 1.

. EIET'E.

Louis B6 ZZ- /Vo rmafn Ma r5716 fizz/622301 5- jiibiiw L. BELL AND N. MARSHALL. METHOD OF AND APPARATUS FOR UTILIZATION OF OBSERVABLE RADIATIONS.

. APPLICATION FILED MAR. 4.1918.

Patented July 26; 1921.

2 SHEETS-SHEET mmwroas Louw Bel? m 5y, 7 a Marshall UNlTD STATES PATENT" OFFICE. 1

LOUIS BELL AND IlORMAN MARSHALL, OF WEST NEWTON, MASSACHUSETTS.

. METHOD OF APPARATUS FOR UTIISIZATION 0F OBSERVABLE RADIATIONS.

Specification of Letters Patent. Pate t d J l 2 Application filed March 4, 1918. 8611a! No. 220,329.

\ To all whom it may concern:

Be it known that we, Louis BELL and Norman MARSHALL, citizens of the United States, residing at West Newton, county of Middlesex, Commonwealth of Massachusetts, I

visible and is especially adapted for use in 4 war where operations are being conducted in the presence of the enemy.

Our invention can be used at sea or in the trenches for visual or other signals which may be recorded in any manner well hiown to those skilled in the art, without danger of enemy discovery,'and is capable of embodi merit in devices easil portable and compactly 'made from rea ily procurable materials.

Our invention is founded upon the fact that there are radiations from a source of high temperature such as an are or incandescent lamp at either side of the visible part of the spectrum, that is, of shorter and longer wave lengths than the visible spectrum. The radiations at either side of the visible spectrum while invisible themselves, follow generally the laws of reflection and refraction of visible light, and produce various fluorescent, che nical, electrical, and other physical effects which can bedetected by suitable receiving apparatus.

In carrying out our invention we project a beam of such rays to a distant point where it is collected, reflected or refracted for observation. e

The method of practising our invention and some convenient forms of apparatus will be more fully set forth in the specification which follows, and the same are'illustrated in the accompanyingdi'awings to which reference is made. i I

F'gure l is a somewhat diagrammatic view of sending and receiving apparatus in accordance with our invention. v

Fig. 2 is a sectional view of a receiving telescope for use in observation and signa Fig. 3'is a sectional detail of an observing eye piece therefor.

Fig. 4 illustrates the use of a photo-electric I cell as a receiving device for such a set.

J gs. 5- and 6 are diagrammatic views s milar to Fig. 1, but illustratin the principlesofc' our inventions as app ied to' Observation alone. F g. 7 is a face view of a field signal set. Figs. 8 and 9 are plan and end views, respectively, of the same, and

Fig. 10 is a diagrammatic view illustratin the recording ofsignals'b hoto ra h fathers have been many di% i ulties in tli e utilization of radiation which by our invention have been avoided or overcome. Such (llfilCllltlfiS are, for instance, the obtaining of a beam of suitable intensity from a source practicable for use in the functions heretofore stated; in the difiiculty of providing receiving apparatus ofysufiicieiit sensitiveness without being at the same'time easily disarranged and uncertain of function; and above all providing both sending and receiving ap paratus sufiiciently portable for the practical operation of observation and signaling. Many substances are extremely opaque to invis ble rays or reflect them badly, and others, which are free from these difiiculties, are practically unobtainable or unusable on a practical scale. For instance, quartz and fluorspar are notoriously transparent to ultra-violet, but neither of them. can be had readily enough or in pieces of sufficient size to render their use practicable.v Rocksalt, the substance most commonly used in the infra red portions of spectra on account of its great permeability to such rays, is extremely sensitive to moisture, and hence out of the question for military urposes,

To certain groups of lIlVlSlj le rays, which might otherwise be desirable glass is'quite opaque, and. with certain others, reflecting substances are undesirable because. they absorb badly; Moreover, certain groups of rays in themselves areundesirable for p'rac: tical use because they are quickly absorbed by the atmosphere, on are obtainable in quantity only from sources not convenient for general use. We have found therefore that each range of invisible rays presents its specific difliculty' in generation, selection, sending and reception, and it is the object of our invention to adapt each to each so as to produce a method and apparatus for the utilization of invisible radiation-of a simple,

.' received upon a fluorescent screen and thereby a similar 'sendin by made lmmediatel optically visible, or upon any of the well known forms of photoelectric detectors, rendering'it detecta le by its electric efi'ects.

We have contemplated three general for of ractice of our IIIVBIlt'iOIlf irst, such an invisible beam may be di rected on-sea or land for the purpose of si aling orders or direetionsbyinterruption o the beam in accordance with a redetermined code.- This end may be e acted by a suitable receiving apparatus at the distant station and the latter may signal back either a'paratus or by suite interception o t e received beam reflected from an ap ropriate surface.

We have found t at,; particularly for si naling purposes, a large part of the invisib e range of radiation is 111 adapted for one or the other of the reasons here suggested, and

- our preferred range of radiation for this urpose consists in those radiations lying tween 400 up. and 350 up. wave lengths,

' which are just too short to be ordinarily visible to the human eyed and et not short enough to be suppressed by or inary refracting or reflectingmedia.

i econd, such an invisible beam-may be turned upon an object, as for instance a friendly ship, provided with diffused or spectral reflecting surfaces b which the beam may be turned back and d rved, so as to recognize the nature and position of the reflecting surface in order to identity or secure its suitable a 'nement, as

in squadron formation. T I Finally, the detection by means of, the invisible ra s of ob'ects otherwise invisible at night. T is maybe accomplished b what is practically a searchli ht of invis i le rays, the portion of" the icked ulp again at or near the sending point y suita le receiving apparatus. TlllS may 7 apply even to rendering visible objects like an enemys ship, otherwise indistinguishable, and to which the beam mustnot be disclosed.

The group of radiations here referred to is relatively easy to i.s 0la te- -in practical -ql111antity, since-it can be screened out from e, rest-,ofJtlie' spectrum by suitable color ;1screens'of relatively simple character.

'portance, we find .by experience that this specialized electric arcs, involvin reserve its am reflected being presence of a searching given lens is materially less for these rays than for the visible *s small a rture place at the proper focal point will let throu h freely a beam of invisible light while irlocking nearly all the visible light, a method which is already familiar to investigators.

"Furthermore, and of great practical imrum, and hence a particular ran e vof radiations is easily obtainable from' incandescent electric lamps or a similar incandescent source, giving a source of energy at once steady, eflicient and convenient, and particularly adaptable to portable use. Experimental work on ultra violet radiations has been heretofore confined almost exclusively to sources specially rich in extreme ultra violet, sources such as highly the use of iron or other metallic termina s, or by 90 use of such sources as vacuum tubes' and mercury arcs, possessing the same characteristics. These sources are none of them convenient for field use; most-of them are unsteady and require the use of highly specialized electrical sources involving voltage not readily obtainable of suflicient strength in portablev appliances. 7

The specified grou of radiations which we prefer house is rec from these objec- .100 tions and is of extremely low visibility. A concentrated beam of this character is completely invisible in its passa e through the air, and invisible also to irect view beyond extremely short distances, compared 105 with that at which it may be detected by means which we have provided and. that meetall the practical requirements of an invisible signaling apparatus. In receivin such a beam, it can be concentrated throng 110 glass lenses without serious loss of intensity, even non-achromatic lenses being suitable on account of the comparatively narrow range of wave lengths.

The fluorescent eye-pieces as applied to 11 spectroscopes in which the beam is spread out on a prism has long been known, but so far as we are aware no attem t has been made'to produce a concentrate fluorescent image upon a fluorescent screen of any kind "12 or. adapted for purposes herein described.

Suitable fluorescent screens may be made of uranyl sulfiate or barium platinum cyanid, the greenish fluorescence of which is characteristic and well known. We believe, 12 I of such material deposited on some transparent material and viewed from the rear or compacted into an opaque screen andviewed from the front ,upon which the light falls. In order to make more clear the actual practice of our invention we have shown in the drawing somewhat diagrammatically certain of the means for practising our invention, and more in detail certain of the actual apfigratus as adapted for field use.

ferring to Fig. 1, we have indicated at A a projector which preferably is in the form of a search light having a source of light a, reflector b, and a selective screen 0. Each projector is in usual ractice accompanied by a receiver which 1s preferably in the form of an observin telescope with an objective d, screen 6, an eye piece 7, all as ap ears in Fig. 1.

he beam projected from A by suitable gredetermined alinement with the receiver at a oint to which the si nal is to be delivered is selectively screenetfby-c. These rays are substantially invisible to the eye but in falling upon the screen e cause the same to fluoresce. This fluorescence 'is observed through the eye piece f.

If now the beam from the projector A is interrupted inaecordance witha predetermined code a signal maybe received as a message. The receivin telescope is shown somewhat more in detail in Fig. 2, in whichthe light is reflected from the mirror 9 on to the fluorescent screen e from which it is observed by the eye piece f.

In Fig. 3 we have shown a detailed modification whereby any telescope maybe fitted as a receivin device in accordance with our invention. t contains the fluorescent screen e which is observed with the eye lens 7 and the field lens P. The field lens may of course be omitted or any otherv familiar form of eye piece substituted for it, provided the screen e is in the principal focus of the telescope for the chosen range of invisible rays, and in the focus of the eye piece for the rays of fluorescence.

Instead of employing an optical receiver such as we have just described and suggested, we may in some instances employ a hoto-electric cell as a receiving device as indicated in Fig. 4. y it In such a device the invisible rays are wel concentrated; by a mirror D ona glass bulb 1 carried on an adjusting stem h which may be conveniently passed throu han aperture in the center of the mirror. e haveindicated at jthe focus of the mirror D, a photoelectric sensitive layerof any suitable metal or alloy, close in front of WlllCll is supported an open work gridk of metal forming the other terminal. From the terminals y and is lead wires Z and l are taken in circuit with the battery m to any convenient device sensitive to minute currents, as for example the galvanometer 'n.

The signal message may also be received (andvrecorded) by the successive exposure of a suitable sensitized film upon which the successive si a1 images are photographed, as shown in ig. 10. 4

Before considering the preferred detail construction of our field projecting equipment, attention may be directed to the matter of observation of an object by nightjby means of the invisible rays projected in accordance with our invention.

In Figs- 5 and 6, we have indicated diagrammatically the use of a projector A, as shown in Fig. 1. We have indicated at C an object reflecting the invisible rays, which reflection is received, collected and observed by the telescope -B or other suitable device in accordance with ourinvention. If the object C is for example a friendly ship, a most advantageous observation may be had by providing it with a reflecting surface 0 which may be convex in order to widen the field and facilitate the observation. The reflecting surface 0 may furthermore be conreflecting surface 0 may be covered by any opaque object such as a hand screen (not shown).

This feature of our invention is capable of a very great variety ofapplications in both marine and land operations. At sea it may be employed not only for the detection of hostile ships but enables friendly ships totrack of the position of each other as as to signal as to position or course.

It, is of course not possible in the scope of the specification to detail all uses and variety of'circumstances under which our device may be employed, and in fact it is believed that man uses not at present thought of will be deve oped in the service by those skilled in keep the departments in which our invention may be employed.

While our invention is capable of many embodiments and a great variety of adaptations to devices already in use, we have provided for immediate service a convenient light R, having suitable s reen Sis mountt ed with universal connectlon T on the box P. \Ve )rovide at U a suitable telegraph key by w ich the circuitof the lamp R may be interrupted by breaking the circuit or by shunting, whichever may be desired, or the front of the lamp A may be screened by perfectly opaque shutters V. For convenience in sighting, a telescopic or other sight maybe mounted on the lamp provided with suitable cross wires w, or other device, for effecting accurate alinement of the lamp R with the receiving device. The lamp R is preferably so mounted on the box P that it ma be turned down into a protective recess t erein or a suitable cover not shown may be hinged to the box top.

The apparatus hereln shown and described may be variously modified and other forms of apparatus may be used in-the practice of our invention. Furthermore, considerable latitude in ray selection may be practised and our invention may be variously utilized as the changin conditions of modern warfare dictate, all without departing from the spirit of. our invention if within the limits of the appended claims.

What we therefore claim and desire to secure by Letters Patent is:

1. A method of signaling which consists in isolatin'g'from a suitable source radiations,

lying between 400 up. and 350w. causing them to be formed into a directed beam, concentrating said beam, and detecting said beam by means of a fluorescent medium and interrupting said beam in accordance with a predetermined code.

2. The method of signaling which consists in forming a radiant beam,'isolating from it radiations lying between wave lengths 400 'up. and 350 up, receiving and focusing said beam upon a medium fluorescing greenish in said rays, and interrupting said beam in accordance with a predetermined code.

' -3'. Ir'r combination for the purpose set forth," an incandescent electric amp, a reflector to form a beam of-the radiation therefrom, means of selecting from said beam.

radiations between wave lengths 400 up. and 3550 au, means for concentrating said radiations upon a greenish-fluorescing screen sensitive thereto, and means for establishing, varying and interrupting said beam in accordance with a predetermined code. 7

4. For the purpose set forth, a source of light, "means for producing a concentrated beam of radiations therefrom, screens selectively absorbing the ordinarily visible spec-.-

trum while transmitting radiation of wave lengths lying between up. and 350 up,

lengths between 400 uaQand 350 up. while I opaque to the ordinary visible spectrum,

means for interrupting 'saidradiation in accordance with a predetermined code and a receiving telescope having a greenish-fluorescing screen in its focus.

6. In combination -forthe purpose. set forth, an incandescin body '0 high temperature furnished with a'reflector having a'mouth, a screen closing the mouth of sai reflector and transmitting radiation of wave".- 1-' lengths between 400 uu'and 350 up. while opaque to the ordinary visible spectrum,

means for interrupting said radiation in ac cordance with a predetermined code and a receiving telescope having a fluorescing screen in. its focus, with a translucent film of solid fluorescing material in the -focus of the objective for, the rays specified and in the focus of the eye piece for-green ra s.

7. A method of utilizing invisible ight rays, consisting in forming a directed beam of rays between 400 up. and 350 up. wave length and collecting said rays for observation on a fluorescent medium.

8. A method of signaling consisting in forming a directed beam of rays from within the llmits of a narrow spectrum band situated between the limit of visibility and vitreous absorption, focusin said ra detecting said focal point by its e act in exciting fluorescence.

9 In a signal apparatus, a transmitter and including means for pro'ecting. a directed Y beam of rays from that and in the ultra violet zone'lying next adjacent the visible spectrum,and a receiver including a screen having a greenish fluorescence under said rays.

10. A method of utilizin rays for signalingor the li e, consisti in formi 400 up. to 350 up. wave lengths and infocusing said rays for observation on a fluorescent medium.

11. 4 In a signal stem, a of radiant energy having a v1treou'sj.inclosure, a vitreous ray filter transmitting rays only between 400 up. and up, a projector for directing the light in a'beam, a control for interrupting the light, an image receivin screen having a responsive fluoresence o greenish character, a lens for focusing the received beam on said screen and an eye piece. for observing said screen.

invisible lighta directed beam of rays of mm 12. In a signal system, a source of radiant the received beam 'upon said screen and an energy having a. vitreous inclosure, a vitreeye piece for observing said screen.

ous screen permeable to rays of wave length In testimony whereof we aflix our signain the region between 400 up and 350 up. but tures in presenceof two Witnesses.

' 5 opaque to the blue end of the visible spec- LOUIS BELL- trum, a projector for directing the light in a beam through said screen, a control for interrupting the light, an image receiv- Witnesses: ing screen having responsive fluorescence 7 VICTORIA LownnN,

NORMAN MARSHALL.

10 of greenish character, a lens for focusing Alarms V. OCONNELL. 

